Learn Hardcore Norwegian: Om vinteren pleide innsjøen å fryse helt, men nå skjer det sjelden. - In winter the lake used to freeze completely, but now that rarely happens.

“I vinter” means “this past winter / last winter” (a specific winter), not winter in general.
“På vinteren” can sometimes be heard, but “om vinteren” is the most natural and idiomatic for “in winter (as a general season)”.

So:

Om vinteren pleide innsjøen å fryse helt = In winter (as a rule, every winter), the lake used to freeze completely.
I vinter frøs innsjøen helt = This (last) winter, the lake froze completely.

What does “pleide” add? Why not just say “Om vinteren frøs innsjøen helt”?

“Pleide” (from å pleie) is used here as a habitual past: it means “used to” or “would (habitually)”.

Om vinteren pleide innsjøen å fryse helt
= In winter, the lake used to freeze completely (but not anymore).

If you say:

Om vinteren frøs innsjøen helt,

this is also grammatical and natural, and context will usually make it clear that it was a regular thing. However, “pleide å” makes the idea of “this was the normal habit in the past, but it has changed” extra explicit, similar to English “used to” versus simple past.

So the original sentence strongly emphasizes the change over time.

What exactly is the structure “pleide innsjøen å fryse”? Why is the verb before the subject?

Norwegian has a V2 (verb-second) word order in main clauses, like German.

The rule:
In a main clause, the finite verb (here: pleide) must come second, no matter what comes first.

The sentence is:

Om vinteren – adverbial phrase (time), placed first.
pleide – finite verb (must be in second position).
innsjøen – subject.
å fryse helt – infinitive phrase (what the lake used to do).

So:

Om vinteren pleide innsjøen å fryse helt. ✅
(Adverbial – Verb – Subject – Rest)

If you start with the subject instead, you get:

Innsjøen pleide å fryse helt om vinteren. ✅
(Subject – Verb – Rest)

But you cannot say:

*Om vinteren innsjøen pleide å fryse helt. ❌
(That breaks the V2 rule.)

What is the difference between “innsjøen” and “en innsjø” here?

Norwegian marks definiteness mostly with a suffix:

en innsjø – a lake (indefinite singular)
innsjøen – the lake (definite singular)

So “innsjøen” literally means “the lake”.

You use the definite form when both speaker and listener know which specific lake is meant (for example, the local lake near the village). If you said:

Om vinteren pleide en innsjø å fryse helt,

it would sound like “A lake used to freeze completely in winter”, as if you’re talking about some random or unknown lake, which doesn’t fit typical real-life context as well.

What does “å fryse” mean here? Isn’t “fryse” also “to feel cold”?

“Å fryse” has two common uses:

Intransitive, about temperature dropping / becoming ice
- Vannet fryser. – The water is freezing / is turning to ice.
- Innsjøen pleide å fryse helt. – The lake used to freeze completely.
Intransitive, about a person feeling cold
- Jeg fryser. – I’m cold / I’m freezing.

In your sentence it clearly means “to freeze, to turn to ice”.
If you want to say someone feels cold, you also say “å fryse”, but context (lake vs. person) makes the meaning clear.

To talk about freezing something (transitive), you can say:

Å fryse ned maten. – To freeze down the food.
Å fryse noe. – To freeze something.

What role does “helt” play in “å fryse helt”?

“Helt” here is an adverb meaning “completely / entirely”.

å fryse – to freeze
å fryse helt – to freeze completely (all the way, over the whole surface/volume)

Other common uses of “helt”:

helt stille – completely quiet
helt ferdig – completely finished
helt tomt – completely empty

So “fryse helt” emphasizes that the lake didn’t just get some ice along the edges; it froze entirely.

In “men nå skjer det sjelden”, what does “det” refer to?

Here “det” is a dummy / placeholder pronoun. It doesn’t refer to a specific “thing” like “it (the lake)”; instead, it stands for the whole situation or event previously mentioned: the lake freezing completely in winter.

You can think of it as:

…but now that (the event) happens rarely.

Norwegian often uses “det” like this in impersonal expressions:

Det regner. – It’s raining.
Det skjer mye rart. – A lot of strange things happen.
Det er kaldt. – It is cold.

So “det” here is more like “that/it (as an event)” than “it (the lake)”.

Why is it “skjer” and not “gjør” in “nå skjer det sjelden”?

Norwegian distinguishes between:

å skje – to happen (like English happen/occur).
å gjøre – to do/make.

So you say:

Hva skjer? – What’s happening?
Hva gjør du? – What are you doing?

In your sentence, we are talking about an event (the lake freezing completely) that happens less often now, so we must use “skje”:

Nå skjer det sjelden. – Now it rarely happens.

Using “gjøre” here would be wrong because nothing is “doing” anything; it’s about the occurrence of an event.

Could you also say “Nå skjer det ikke ofte” instead of “Nå skjer det sjelden”?

Yes, you could:

Nå skjer det ikke ofte. – Now it doesn’t happen often.
Nå skjer det sjelden. – Now it happens rarely.

Both are grammatical and mean almost the same thing.
Differences:

“sjelden” is a single adverb that directly means “rarely / seldom”.
“ikke ofte” is a bit more literal: “not often”.

Stylistically, “sjelden” is more compact and a bit more neutral; “ikke ofte” can sound slightly softer or less definite in some contexts, but in this sentence, they’re very close in meaning.

How does “sjelden” work grammatically? Where can it go in the sentence?

“Sjelden” is an adverb of frequency: “rarely / seldom”.

In your sentence:

Nå skjer det sjelden. – Now it happens rarely.

Common positions:

After the verb (and subject if there is inversion):
- Han kommer sjelden. – He rarely comes.
- Nå skjeler det sjelden. – Now it rarely happens.
Before the verb (less common, often for emphasis or in writing):
- Sjelden kommer han tidlig. – Rarely does he come early. (somewhat literary / emphatic)

In normal everyday speech, “subject – verb – sjelden – rest” or “adverbial – verb – subject – sjelden – rest” is typical:

Han besøker oss sjelden.
Om sommeren regner det sjelden.

Why is it “pleide” (past) in the first part but “skjer” (present) in the second?

The two clauses talk about different time frames:

“Om vinteren pleide innsjøen å fryse helt” –
Past habit: this was the old normal. It happened regularly before.
“men nå skjer det sjelden” –
Present truth: nowadays this event rarely happens.

So:

pleide = used to, a pattern in the past.
skjer = happens (now, in general current time).

If you used past in both:

Om vinteren pleide innsjøen å fryse helt, men da skjedde det sjelden.

you would be saying something like:
“In winter the lake used to freeze completely, but (even back then) it rarely happened”, which is contradictory. The original contrast is: before vs. now.

Why is it “å fryse” and not “og fryse”? They look very similar.

This is a very common confusion.

“å” is the infinitive marker, like English “to” before a verb.
- å fryse – to freeze
- å spise – to eat
- å sove – to sleep
“og” is the conjunction “and”.
- vann og is – water and ice
- å spise og drikke – to eat and drink

In your sentence:

pleide innsjøen å fryse helt
= the lake used to freeze completely.

You must use “å” before “fryse” because it’s an infinitive following “pleide”.
“og fryse” would mean “and freeze”, which doesn’t fit the structure here.

Could you also say “Om vinteren brukte innsjøen å fryse helt” instead of “pleide innsjøen å fryse helt”?

Yes, in colloquial Norwegian many people say:

Om vinteren brukte innsjøen å fryse helt.

Here “brukte å” plays the same role as “pleide å”, meaning “used to” (habitual past).

However:

Some style guides and teachers prefer “pleide å” for this habitual meaning and regard “brukte å” in this sense as less formal or less standard in written Bokmål.
In spoken language, “brukte å” is very common and widely understood.

So for formal writing or exams, “pleide å” is the safest choice.
For everyday speech, both are fine, depending on region and personal style.

Why is there a comma before “men”?

In Norwegian, as in English, “men” (“but”) usually introduces a new main clause that contrasts with the previous one.

Your sentence has two main clauses:

Om vinteren pleide innsjøen å fryse helt
(men) nå skjer det sjelden

They are joined by the coordinating conjunction “men”, so they are separated by a comma:

Om vinteren pleide innsjøen å fryse helt, men nå skjer det sjelden.

This is similar to English:
“In the winter the lake used to freeze completely, but now it rarely happens.”